Apparatus and methods for txop duration field in phy header

ABSTRACT

A method implemented by a station (STA) in a Wireless Local Area Network (WLAN) to disregard a Network Allocation Vector (NAV) maintained by the STA. The method includes receiving a first frame from an Access Point (AP), determining whether the NAV maintained by the STA was previously set using a duration indicated in a second frame that (1) was received by the STA prior to receiving the first frame and (2) originated from the AP, and transmitting a third frame to the AP as an immediate response to the first frame without considering the NAV maintained by the STA when a determination is made that the NAV maintained by the STA was previously set using the duration indicated in the second frame that originated from the AP.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/284,929, filed Feb. 25, 2019, which is a divisional of U.S.application Ser. No. 15/278,597, filed Sep. 28, 2016 (now U.S. Pat. No.10,257,857, issued Apr. 9, 2019), which claims the benefit of U.S.Provisional Application No. 62/240,454, filed Oct. 12, 2015, and U.S.Provisional Application No. 62/233,881, filed Sep. 28, 2015, which arehereby incorporated by reference.

FIELD OF INVENTION

The embodiments described herein related to the field of Wireless LocalArea Network (WLAN) operation. More specifically, the embodimentsdescribed herein relate to the maintenance and use of Network AllocationVector (NAV) in a High Efficiency (HE) Wireless Local Area Network(WLAN). Other embodiments are also disclosed.

BACKGROUND

Institute of Electrical and Electronics Engineers (IEEE) 802.11 is a setof physical and Media Access Control (MAC) specifications forimplementing Wireless Local Area Network (WLAN) communications. Thesespecifications provide the basis for wireless network products using theWi-Fi brand managed and defined by the Wi-Fi Alliance. Thespecifications define the use of the 2.400-2.500 GHz as well as the4.915-5.825 GHz bands. These spectrum bands are commonly referred to asthe 2.4 GHz and 5 GHz bands. Each spectrum is subdivided into channelswith a center frequency and bandwidth. The 2.4 GHz band is divided into14 channels spaced 5 MHz apart, though some countries regulate theavailability of these channels. The 5 GHz band is more heavily regulatedthan the 2.4 GHz band and the spacing of channels varies across thespectrum with a minimum of a 5 MHz spacing dependent on the regulationsof the respective country or territory.

WLAN devices are currently being deployed in diverse environments. Theseenvironments are characterized by the existence of many Access Points(APs) and non-AP stations (STAs) in geographically limited areas.Increased interference from neighboring devices gives rise toperformance degradation. Additionally, WLAN devices are increasinglyrequired to support a variety of applications such as video, cloudaccess, and offloading. Video traffic, in particular, is expected to bethe dominant type of traffic in WLAN deployments. With the real-timerequirements of some of these applications, WLAN users demand improvedperformance.

A WLAN device typically employs a carrier sense mechanism to determinewhether it can transmit data over a wireless medium. The distributednature of 802.11 WLANs makes the carrier sense mechanism very importantfor reducing the amount of collisions in the WLAN. The physical carriersense mechanism of a WLAN device is responsible for detectingtransmissions of other WLAN devices. However, it may be impossible for aWLAN device to detect all of the transmissions that may collide with itsown transmission. For example, a WLAN device which is a long distanceaway from another WLAN device that is transmitting data may determinethat the wireless medium is idle and begin transmitting data as well. Toovercome such hidden node problems, a Network Allocation Vector (NAV)has been introduced. NAV maintains a prediction of future traffic on thewireless medium based on duration information captured from PhysicalLayer Protocol Data Units (PPDUs).

In a task group called Institute of Electrical and Electronics Engineers(IEEE) 802.11ax, High Efficiency WLAN (HEW) standardization is underdiscussion. The HEW aims at improving performance felt by usersdemanding high-capacity and high-rate services. The HEW may supportuplink (UL) and downlink (DL) multi-user (MU) simultaneoustransmissions, which includes Multi-User Multiple-Input Multiple-Output(MU-MIMO) and Orthogonal Frequency Division Multiple Access (OFDMA)transmissions. The HEW may also support new Clear Channel Assessment(CCA) levels and deferral rules to improve Overlapping Basic Service Set(OBSS) operation in dense environments. Employing existing NAVtechniques in the HEW may result in unintended inefficiencies.

SUMMARY

A method is implemented by a station (STA) in a Wireless Local AreaNetwork (WLAN) to update a Network Allocation Vector (NAV) maintained bythe STA. The method includes receiving a first Physical Layer ProtocolData Unit (PPDU), determining whether a duration indicated in a controlfield of a preamble portion of the first PPDU is greater than a currentNAV value, determining whether the first PPDU is received as animmediate response to a second PPDU previously transmitted by the STA,and updating the NAV maintained by the STA using the duration indicatedin the control field of the preamble portion of the first PPDU inresponse to a determination that the duration indicated in the controlfield of the preamble portion of the first PPDU is greater than thecurrent NAV value and the first PPDU is not received as an immediateresponse to the second PPDU previously transmitted by the STA.

A method is implemented by a station (STA) in a Wireless Local AreaNetwork (WLAN) to disregard a Network Allocation Vector (NAV) maintainedby the STA. The method includes receiving a first Physical LayerProtocol Data Unit (PPDU) from an Access Point (AP), where the firstPPDU elicits an immediate response from the STA, determining whether theNAV maintained by the STA was previously set using a duration indicatedin a second PPDU that originated from a same Basic Service Set (BSS) asa BSS that the STA is associated with, and transmitting a third PPDU tothe AP as an immediate response to the first PPDU without regard for theNAV maintained by the STA in response to a determination that the NAVmaintained by the STA was previously set using the duration indicated inthe second PPDU.

A network device configured to function as a station (STA) in a WirelessLocal Area Network (WLAN) to update a Network Allocation Vector (NAV)maintained by the STA. The network device includes a Radio Frequency(RF) transceiver, a set of one or more processors, and a non-transitorymachine-readable storage medium having stored therein a NAV component.The NAV component, when executed by the set of one or more processors,causes the network device to receive a first Physical Layer ProtocolData Unit (PPDU), determine whether a duration indicated in a controlfield of a preamble portion of the first PPDU is greater than a currentNAV value, determine whether the first PPDU is received as an immediateresponse to a second PPDU previously transmitted by the STA, and updatethe NAV maintained by the STA using the duration indicated in thecontrol field of the preamble portion of the first PPDU in response to adetermination that the duration indicated in the control field of thepreamble portion of the first PPDU is greater than the current NAV valueand the first PPDU is not received as an immediate response to thesecond PPDU previously transmitted by the STA.

A network device configured to function as a station (STA) in a WirelessLocal Area Network (WLAN) to disregard a Network Allocation Vector (NAV)maintained by the STA. The network device includes a Radio Frequency(RF) transceiver, a set of one or more processors, and a non-transitorymachine-readable storage medium having stored therein a NAV component.The NAV component, when executed by the set of one or more processors,causes the network device to receive a first Physical Layer ProtocolData Unit (PPDU) from an Access Point (AP), where the first PPDU elicitsan immediate response from the STA, determine whether the NAV maintainedby the STA was previously set using a duration indicated in a secondPPDU that originated from a same Basic Service Set (BSS) as a BSS thatthe STA is associated with, and transmit a third PPDU to the AP as animmediate response to the first PPDU without regard for the NAVmaintained by the STA in response to a determination that the NAVmaintained by the STA was previously set using the duration indicated inthe second PPDU.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments are illustrated by way of example, and not by way oflimitation, in the figures of the accompanying drawings in which likereferences indicate similar elements. It should be noted that differentreferences to “an” or “one” embodiment in this specification are notnecessarily to the same embodiment, and such references mean at leastone. Further, when a particular feature, structure, or characteristic isdescribed in connection with an embodiment, it is submitted that it iswithin the knowledge of one skilled in the art to affect such feature,structure, or characteristic in connection with other embodimentswhether or not explicitly described.

FIG. 1 is a flow diagram illustrating operations for setting a NAV,according to some embodiments.

FIG. 2A is a diagram illustrating a scenario where an AP sets its NAVwhen it is unable to successfully decode a payload portion of a UL MUPPDU, according to some embodiments.

FIG. 2B is a diagram illustrating a scenario where an AP sets its NAVwhen there is a payload error in an ACK frame or Block ACK frame,according to some embodiments.

FIG. 2C is a diagram illustrating a scenario where an AP sets its NAVwhen there is a payload error in a compressed beamforming frame,according to some embodiments.

FIG. 2D is a diagram illustrating a scenario where an AP sets its NAVwhen there is a payload error in compressed beamforming framestransmitted in MU manner, according to some embodiments.

FIG. 3A is a diagram illustrating a scenario where an AP refrains fromsetting its NAV when it is unable to successfully decode a payloadportion of a UL MU PPDU, according to some embodiments.

FIG. 3B is a diagram illustrating a scenario where an AP refrains fromsetting its NAV when there is a payload error in an ACK frame or BlockACK frame, according to some embodiments.

FIG. 3C is a diagram illustrating a scenario where an AP refrains fromsetting its NAV when there is a payload error in a compressedbeamforming frame, according to some embodiments.

FIG. 3D is a diagram illustrating a scenario where an AP refrains fromsetting its NAV when there is a payload error in compressed beamformingframes transmitted in MU manner, according to some embodiments.

FIG. 4 is a flow diagram of a process for maintaining a NAV, accordingto some embodiments.

FIG. 5 is a diagram illustrating a scenario where a STA does not respondto a trigger frame due to its NAV being set, according to someembodiments.

FIG. 6 is a diagram illustrating a scenario where a STA responds to atrigger frame without regard to its NAV, according to some embodiments.

FIG. 7 is a flow diagram of a process for using a NAV, according to someembodiments.

FIG. 8 is a block diagram of a network device implementing a STA or APthat executes a NAV component, according to some embodiments.

FIG. 9 is a block diagram of a WLAN, according to some embodiments.

FIG. 10 is a schematic block diagram exemplifying a transmitting signalprocessor in a WLAN device, according to some embodiments.

FIG. 11 is a schematic block diagram exemplifying a receiving signalprocessing unit in a WLAN device, according to some embodiments.

FIG. 12 is a timing diagram providing an example of the Carrier SenseMultiple Access/Collision Avoidance (CSMA/CA) transmission procedure,according to some embodiments.

DETAILED DESCRIPTION

The embodiments disclosed herein provide methods and apparatus for themaintenance and use of a Network Allocation Vector (NAV) in a HighEfficiency (HE) Wireless Local Area Network (WLAN) that improvesefficiency in the HE WLAN. An embodiment is a method implemented by astation (STA) in a WLAN. The method includes receiving a first PhysicalLayer Protocol Data Unit (PPDU), determining whether a durationindicated in a control field of a preamble portion of the first PPDU isgreater than a current NAV value, determining whether the first PPDU isreceived as an immediate response to a second PPDU previouslytransmitted by the STA, and updating a NAV maintained by the STA usingthe duration indicated in the control field of the preamble portion ofthe first PPDU in response to a determination that the durationindicated in the control field of the preamble portion of the first PPDUis greater than the current NAV value and the first PPDU is not receivedas an immediate response to a second PPDU previously transmitted by theSTA. Another embodiment is a method implemented by a STA in a WLAN. Themethod includes receiving a first PPDU from an Access Point (AP), wherethe first PPDU elicits an immediate response from the STA, determiningwhether a NAV maintained by the STA was previously set using a durationindicated in a second PPDU that originated from a same Basic Service Set(BSS) as a BSS associated with the STA, and transmitting a third PPDU tothe AP as an immediate response to the first PPDU without regard for theNAV maintained by the STA in response to a determination that the NAVmaintained by the STA was previously set using the duration indicated inthe second PPDU. Other embodiments are also described and claimed.

In the following description, numerous specific details are set forth.However, it is understood that embodiments described herein may bepracticed without these specific details. In other instances, well-knowncircuits, structures and techniques have not been shown in detail inorder not to obscure the understanding of this description. It will beappreciated, however, by one skilled in the art that the embodimentsdescribed herein may be practiced without such specific details. Thoseof ordinary skill in the art, with the included descriptions, will beable to implement appropriate functionality without undueexperimentation.

References in the specification to “one embodiment,” “an embodiment,”“an example embodiment,” etc., indicate that the embodiment describedmay include a particular feature, structure, or characteristic, butevery embodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to effect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed.

In the following description and claims, the terms “coupled” and“connected,” along with their derivatives, may be used. It should beunderstood that these terms are not intended as synonyms for each other.“Coupled” is used to indicate that two or more elements, which may ormay not be in direct physical or electrical contact with each other,co-operate or interact with each other. “Connected” is used to indicatethe establishment of communication between two or more elements that arecoupled with each other. A “set,” as used herein refers to any positivewhole number of items including one item.

An electronic device stores and transmits (internally and/or with otherelectronic devices over a network) code (which is composed of softwareinstructions and which is sometimes referred to as computer program codeor a computer program) and/or data using machine-readable media (alsocalled computer-readable media), such as non-transitory machine-readablemedia (e.g., machine-readable storage media such as magnetic disks,optical disks, read only memory, flash memory devices, phase changememory) and transitory machine-readable transmission media (also calleda carrier) (e.g., electrical, optical, radio, acoustical or other formof propagated signals—such as carrier waves, infrared signals). Thus, anelectronic device (e.g., a computer) includes hardware and software,such as a set of one or more processors coupled to one or morenon-transitory machine-readable storage media (to store code forexecution on the set of processors and data) and a set of one or morephysical network interface(s) to establish network connections (totransmit code and/or data using propagating signals). Put another way, atypical electronic device includes memory comprising non-volatile memory(containing code regardless of whether the electronic device is on oroff) and volatile memory (e.g., dynamic random access memory (DRAM),static random access memory (SRAM)), and while the electronic device isturned on that part of the code that is currently being executed iscopied from the slower non-volatile memory into the volatile memory(often organized in a hierarchy) for execution by the processors of theelectronic device.

A network device (ND) is an electronic device that communicativelyinterconnects other electronic devices on the network (e.g., othernetwork devices, end-user devices). Some network devices are “multipleservices network devices” that provide support for multiple networkingfunctions (e.g., routing, bridging, switching, Layer 2 aggregation,session border control, Quality of Service, and/or subscribermanagement), and/or provide support for multiple application services(e.g., data, voice, and video). Network devices or network elements caninclude APs and non-AP STAs in wireless communications systems such as aWLAN. STAs are devices connected to and communicating in a WLANincluding client or user devices that connect to the WLAN via APs. APsare network devices that may be specialized wireless access points thatcan communicate with other network devices in the WLAN via the wirelessmedium or via wired connections. APs may be considered to be a type ofSTA. A non-AP STA or AP may be referred to herein as a WLAN device orSTA.

As mentioned above, in a task group called Institute of Electrical andElectronics Engineers (IEEE) 802.11ax, HE WLAN (HEW) standardization isunder discussion. The HEW may support uplink (UL) and downlink (DL)multi-user (MU) simultaneous transmissions. In an MU simultaneoustransmission, multiple frames are transmitted to or from multiple STAssimultaneously using different resources, where the different resourcescould be different frequency resources in the case of an OrthogonalFrequency Division Multiple Access (OFDMA) transmission or differentspatial streams in the case of a Multi-User Multiple-Input MultipleOutput (MU-MIMO) transmission. Examples of MU simultaneous transmissioninclude DL-OFDMA, DL MU-MIMO, UL-OFDMA, and UL-MU-MIMO.

An AP may initiate a UL MU simultaneous transmission by transmitting atrigger frame (sometimes referred to as a UL-Poll frame) to a set ofSTAs that are to participate in the UL MU simultaneous transmission. Thetrigger frame may include information pertaining to the UL MUsimultaneous transmission such as the assignment of transmissionresources to STAs. Based on this information, the STAs may transmittheir respective frames to the AP essentially simultaneously using anassigned transmission resource. If the AP successfully receives anddecodes the uplink frames transmitted by the STAs, the AP may transmitacknowledgement (ACK) frames to the STAs.

The HEW may also support new Clear Channel Assessment (CCA) levels anddeferral rules to improve Overlapping Basic Service Set (OBSS) operationin dense environments. For example, in one embodiment, when a STAreceives a PPDU which results in that the STA determines the wirelessmedium is busy, the STA decodes the PPDU and checks the contents in theBSS color field of the HE-SIG-A field or the MAC address in the MACheader to determine whether the PPDU is an intra-BSS PPDU or aninter-BSS PPDU with respect to the STA. As used herein, a PPDU is anintra-BSS PPDU with respect to a STA if the PPDU originated from a WLANdevice that is associated with the same BSS as the STA. As used herein,a PPDU is an inter-BSS PPDU with respect to a STA if the PPDU originatedfrom a WLAN device that is associated with a different BSS than the STA.The STA may suspend the backoff countdown process during the time thatis taken by the STA to determine whether the PPDU is an intra-BSS PPDUor an inter-BSS PPDU. If the STA determines that the received PPDU is aninter-BSS PPDU, the STA may use an OBSS Packet Detection (PD) level thatis greater than the minimum receive sensitivity level. If the ReceiveSignal Strength Indicator (RSSI) of the received PPDU is below the OBSSPD level, then the STA may determine that the wireless medium isavailable for use. However, if the RSSI of the received PPDU is abovethe OBSS PD level, then the STA may determine that the wireless mediumis busy and set/update its NAV.

According to current 802.11 specification, NAV is typically set/updatedusing a duration indicated in a Physical Layer Service Data Unit (PSDU)(e.g., in MAC header). However, in some cases a STA may not be able tosuccessfully decode a PSDU from a PPDU, and thus may not be able toobtain duration information. Embodiments described herein may overcomethe problem described above by using the duration indicated in the TXOPduration field of the HE-SIG-A field of the preamble portion of the PPDUto set/update its NAV. The preamble portion of a PPDU is typicallyencoded using a lower Modulation Coding Scheme (MCS) than the payloadportion (which includes a PSDU), and thus is more likely to besuccessfully decoded compared to the payload portion.

FIG. 1 is a flow diagram illustrating operations for setting/updating aNAV, according to some embodiments. When a STA (e.g., AP or non-AP STA)receives a PPDU which results in that the STA determines the wirelessmedium is busy, the STA decodes the PPDU and checks the contents of theHE-SIG-A field to determine whether the PPDU is an intra-BSS PPDU or aninter-BSS PPDU (e.g., by checking the BSS color field of the HE-SIG-Afield). The STA may suspend the backoff countdown process during thetime that is taken by the STA to determine whether the PPDU is anintra-BSS PPDU or an inter-BSS PPDU. The HE-SIG-A field may include anindication of a BSS color. The BSS color helps identify a BSS associatedwith the STA that transmitted the PPDU. If the BSS color indicated inthe HE-SIG-A field matches the BSS color of the BSS associated with thereceiving STA, the receiving STA regards the PPDU as an intra-BSS PPDUand sets/updates its NAV using the duration indicated in the TXOPduration field of the HE-SIG-A field, if this new NAV is greater thanthe existing NAV (e.g., current NAV value). If the BSS color indicatedin the HE-SIG-A field does not match the BSS color of the BSS associatedwith the receiving STA, the receiving STA regards the PPDU as aninter-BSS PPDU and is allowed to adjust the OBSS PD level (e.g., to apredetermined level) according to a function of transmit power control.If the received power (e.g., RSSI) is less than the OBSS PD level, thereceiving STA ignores its NAV. Then, the receiving STA determines thatthe wireless medium is idle and resumes backoff countdown process duringDistributed Coordination Function (DCF) Interframe space (DIFS) periodor Extended Interframe space (EIFS) period to be ready for spatial reuse(SR). If the received power is equal to or greater than the OBSS PDlevel, then the receiving STA sets/updates its NAV using the durationindicated in the TXOP duration field of the HE-SIG-A field, if this newNAV is greater than the existing NAV.

According to some embodiments, the above operations for setting/updatinga NAV can be generalized as follows. When a STA (e.g., AP or non-AP STA)receives a PPDU, the STA determines whether the PPDU is an inter-BSSPPDU or an inter-BSS PPDU. This determination can be made based on BSSindication bits (e.g. BSS color bits) included in a control field of thePPDU. If the STA determines that the PPDU is an intra-BSS PPDU, the STAsets/updates its NAV using a duration indicated in the control field ofthe PPDU, if this new NAV is greater than the existing NAV. However, ifthe STA determines that the PPDU is an inter-BSS PPDU, the STAdetermines whether the received power (e.g., RSSI) is less than the OBSSPD level. If so, the STA ignores its NAV (and thus may use the wirelessmedium to transmit, given other conditions are met). However, if the STAdetermines that the received power is equal to or greater than the OBSSPD level, the STA sets/updates its NAV using the duration indicated in aduration field of a control field of the PPDU, if this new NAV isgreater than the existing NAV. In one embodiment, the BSS indicationbits are BSS color bits (e.g., in a BSS color field). In one embodiment,the control field is an HE-SIG-A field. In one embodiment, the durationfield is a TXOP duration field.

According to current 802.11 specification, when a STA receives a framewhere the MAC address indicated in the Receiver Address (RA) field ofthe MAC header matches the MAC address of the STA, the STA does notset/update its NAV. However, for all other received frames (where theMAC address indicated in the RA field does not match the MAC address ofthe STA or where the STA does not successfully decode the payload), theSTA sets/updates its NAV using the duration indicated in the PSDU, ifthis new NAV is greater than the existing NAV. In some cases, the STA isunable to successfully decode the payload (e.g., PSDU) of the PPDU andthus the STA may not be able to obtain the MAC address indicated in theRA field of the MAC header. This may cause the STA to set/update its NAVeven when the STA is the intended recipient of the PPDU, which canresult in inefficient operation in a WLAN (e.g., HEW), as describedbelow.

FIG. 2A is a diagram illustrating a scenario where an AP sets/updatesits NAV when it is unable to successfully decode a payload portion of aUL MU PPDU, according to some embodiments. For illustration purposes,the operations in this diagram and some of the other diagrams will bedescribed in the context of a simple WLAN (e.g., HEW) that includes anAP and one or more non-AP STAs (e.g., STA1, STA2, STA3, and STA4). Itshould be understood, however, that the principles and conceptsdescribed herein are not limited thereto. Also, for sake of simplicityand clarity, ACK and/or Block ACK procedures may be omitted from thediagrams when they are not necessary for understanding the principlesand concepts described herein. In this exemplary scenario shown in FIG.2A, the AP attempts to receive UL frames from four STAs (e.g., STA1,STA2, STA3, and STA4) within a TXOP. The AP transmits a Request to Send(RTS) frame that elicits Clear to Send (CTS) frames from the four STAsand then receives CTS frames from the respective STAs as part of a UL MUsimultaneous transmission. The exchange of the RTS frame and the CTSframes helps avoid any hidden node problems.

The AP then transmits a trigger frame to STA1 and STA2 that elicits anUL MU simultaneous transmission from those STAs. In response, STA1 andSTA2 transmit an UL MU PPDU to the AP, where the UL MU PPDU includes apreamble portion and a payload portion. In this example, the AP is ableto successfully decode the preamble portion, but is unable tosuccessfully decode the payload portion of the UL MU PPDU due to anerror. As such, the AP is unable to obtain information included in theRA field and the Transmitter Address (TA) field. In this example, theBSS color indicated in the preamble portion of the UL MU PPDU matchesthe BSS color of the BSS associated with the AP. Thus, following currentrules, the AP may set/update its NAV using the duration indicated in thepreamble portion of the UL MU PPDU. However, this is not an intendedprocedure since the AP is the intended recipient of the UL MU PPDU.

A similar problem can occur when there is a payload error in an ACKframe or Block ACK (BA) frame. For example, as shown in FIG. 2B,following an exchange of RTS and CTS frames, the AP transmits a dataframe to STA1. In response, STA1 transmits an ACK/BA frame to the AP.However, in this example, due to a payload error, the AP is unable toobtain information included in the RA/TA fields of the ACK/BA frame(e.g., AP is only able to successfully decode the preamble portion ofthe PPDU that includes the ACK/BA frame). As a result, the AP may notknow that the ACK/BA frame is intended for itself. As such, the AP mayset/update its NAV, which is not the intended procedure.

A similar problem can also occur during a Channel State Information(CSI) feedback procedure (commonly referred to as a sounding procedure).As shown in FIG. 2C, the AP (which is the beamformer in this example)initiates a sounding procedure by transmitting a Non-Data PacketAnnouncement (NDPA) followed by a Non-Data Packet (NDP). In response,STA1 (which is a beamformee in this example) transmits a compressedbeamforming frame to the AP. The AP then transmits a beamforming reportpoll frame, which causes STA2 (which is another beamformee in thisexample) to transmit a compressed beamforming frame to the AP. However,in this example, due to a payload error, the AP is unable to obtaininformation included in the RA/TA fields of this compressed beamformingframe (e.g., AP is only able to successfully decode the preamble portionof the PPDU that includes this compressed beamforming frame). As aresult, the AP may not know that this compressed beamforming frame isintended for itself. As such, the AP may set/update its NAV, which isnot the intended procedure. In some cases, as shown in FIG. 2D, multipleSTAs can transmit their respective compressed beamforming frames to theAP simultaneously as part of a UL MU simultaneous transmission (e.g., ULOF-DMA or UL MU-MIMO transmissions) after receiving a trigger frame fromthe AP that facilitates resource assignment among STAs such thattransmissions do not overlap in the frequency domain and/or spatialdomain. In this example, due to a payload error, the AP is unable toobtain information included in the RA/TA fields of these compressedbeamforming frames. As a result, the AP may not know that the compressedbeamforming frames are intended for itself. As such, the AP mayset/update its NAV, which is not the intended procedure.

Embodiments described herein may overcome the problems described aboveby having the AP refrain from setting/updating its NAV when the AP isunable to successfully decode the payload portion of a PPDU if the APdetermines that the PPDU is received as a response to a PPDU previouslytransmitted by the AP. In one embodiment, the AP may determine that thePPDU was received as a response to a PPDU previously transmitted by theAP if the PPDU is received a given Interframe Space (xIFS—e.g., ShortInterframe Space (SIFS)) time after transmitting the initial PPDU and/orbased on one or more characteristics of the received PPDU.

According to some embodiments, operations for setting/updating a NAV canbe as follows. When a STA (e.g., AP or non-AP STA) receives a PPDU, theSTA determines whether the MAC address indicated in the RA field of theMAC header matches the MAC address of the STA. If so, the STA determinesthat the STA is an intended recipient of the UL MU PPDU. Accordingly,the STA does not set/update its NAV. However, if the STA determines thatthe MAC address indicated in the RA field of the MAC header does notmatch the MAC address of the STA, the STA determines that the PPDU isnot an intended recipient and sets or updates its NAV.

The STA determines that the PPDU is an intra-BSS PPDU when BSS colorindicated by BSS indication bits in a control field of the PPDU matchesthe BSS color of the BSS that the STA is associated with, and in thiscase, the STA may update its NAV using a duration indicated in thecontrol field of the PPDU, if this new NAV is greater than the existingNAV, unless certain conditions apply. For example, in one embodiment,the STA does not set or update its NAV if the STA determines that thePPDU was received as a response to a PPDU previously transmitted by theSTA. In one embodiment, the STA may determine that the PPDU is receivedas a response to a PPDU previously transmitted by the STA if the PPDU isreceived xIFS time after transmitting the initial PPDU.

The STA determines that the PPDU is an inter-BSS PPDU when BSS colorindicated by BSS indication bits in the control field of the PPDU doesnot match the BSS color of the BSS that the STA is associated with, andin this case, the STA determines whether the received power (e.g., RSSI)is less than the OBSS PD level. If so, the STA ignores its existing NAV(and thus may use the wireless medium to transmit, given otherconditions are met). However, if the STA determines that the receivedpower is equal to or greater than the OBSS PD level, the STA updates itsNAV using the duration indicated in a duration field of a control fieldof the PPDU, if this new NAV is greater than the existing NAV.

In one embodiment, the received PPDU includes a UL data frame (e.g., MUor Single-User (SU)) (e.g., as shown in FIG. 2A). In one embodiment, thereceived PPDU includes an ACK or BA frame (e.g., as shown in FIG. 2B).In one embodiment, the received PPDU includes a compressed beamformingframe (e.g., as shown in FIGS. 2C and 2D). In one embodiment, the BSSindication bits are BSS color bits (e.g., in a BSS color field). In oneembodiment, the control field is an HE-SIG-A field. In one embodiment,the duration field is a TXOP duration field. In one embodiment, xIFS isSIFS.

In one embodiment, an AP can determine that a PPDU is received as animmediate response to a trigger frame previously transmitted by the APbased on information included in the L-SIG field (e.g. the length of thereceived PPDU) or HE-SIG-A field (e.g., UL/DL, BSS color, bandwidth,etc.) of the received PPDU. Since the AP may have specified the variousparameters pertaining to the UL MU simultaneous transmission (that theSTAs should follow) in the trigger frame, the AP may have some idearegarding the expected characteristics of the response. Based on theabove information, the AP may determine that the received PPDU isreceived as an immediate response to the trigger frame without havingthe information in the TA/RA fields of the PPDU.

In one embodiment, an AP can determine that a PPDU is received as animmediate response to a frame previously transmitted by the AP based oninformation included in the L-SIG field (e.g., the length of thereceived PPDU) or HE-SIG-A field (e.g., uplink/downlink, BSS color,bandwidth, etc.) of the received PPDU. For example, the AP may have someidea regarding the expected characteristics and length of the ACK frame.Based on the above information, the AP may determine that the receivedPPDU includes an ACK frame that is an immediate response to thepreviously transmitted frame without having the information in the TA/RAfields of the PPDU.

In one embodiment, an AP can determine that a PPDU is received as animmediate response to a beamforming report poll frame previouslytransmitted by the AP based on information included in the L-SIG field(e.g., the length of the received PPDU) or HE-SIG-A field (e.g.,uplink/downlink, BSS color, bandwidth, etc.) of the received PPDU. Forexample, the AP may have some idea regarding the expectedcharacteristics and length of the compressed beamforming frame. Based onthe above information, the AP may determine that the received PPDUincludes a compressed beamforming frame that is received as an immediateresponse to the beamforming report poll frame without having theinformation in the TA/RA fields of the PPDU.

With the NAV setting operations described above, the AP may avoidunnecessarily setting/updating its NAV. For example, as shown in FIG.3A, which corresponds to the scenario described with reference to FIG.2A, when the AP receives the UL MU PPDU but is unable to successfullydecode the payload portion of the UL MU PPDU, the AP may refrain fromsetting/updating its NAV since the AP may recognize that the UL MU PPDUis received as an immediate response to the trigger frame that the APpreviously transmitted (e.g., based on the UL MU PPDU being receivedxIFS time after transmitting the trigger frame and/or based on one ormore characteristics of the UL MU PPDU).

Similarly, as shown in FIG. 3B, which corresponds to the scenariodescribed with reference to FIG. 2B, when the AP receives the ACK/BAframe but is unable to successfully decode the payload portion of theACK/BA frame, the AP may refrain from setting/updating its NAV since theAP may recognize that the ACK/BA frame is received as an immediateresponse to the data frame that the AP previously transmitted.

Similarly, as shown in FIG. 3C, which corresponds to the scenariodescribed with reference to FIG. 2C, when the AP receives the compressedbeamforming frame but is unable to successfully decode the payloadportion of the compressed beamforming frame, the AP may refrain fromsetting/updating its NAV since the AP may recognize that the compressedbeamforming frame is received as an immediate response to thebeamforming report poll frame that the AP previously transmitted.

Similarly, as shown in FIG. 3D, which corresponds to the scenariodescribed with reference to FIG. 2D, when the AP receives the compressedbeamforming frames but is unable to successfully decode the payloadportion of these compressed beamforming frames, the AP may refrain fromsetting/updating its NAV since the AP may recognize that thesecompressed beamforming frames are received as an immediate response tothe trigger frame that the AP previously transmitted.

FIG. 4 is a flow diagram of a process for maintaining a NAV, accordingto some embodiments. In one embodiment, the operations of the flowdiagram may be performed by a network device functioning as a STA (e.g.,AP or non-AP STA) in a wireless communications network (e.g., a WLAN).The operations in this flow diagram and other flow diagrams will bedescribed with reference to the exemplary embodiments of the otherfigures. However, it should be understood that the operations of theflow diagrams can be performed by embodiments other than those discussedwith reference to the other figures, and the embodiments discussed withreference to these other figures can perform operations different thanthose discussed with reference to the flow diagrams.

In one embodiment, the process is initiated when the STA receives afirst PPDU, where the STA is unable to (successfully) decode a payloadportion of the first PPDU (block 410). Although the STA is unable tosuccessfully decode the payload portion of the first PPDU, the STA maybe able to successfully decode the preamble portion of the first PPDU.

The STA determines whether the BSS color indicated in the control fieldof the preamble portion of the first PPDU matches the BSS color of theBSS that the STA is associated with (decision block 420). If so (e.g.,first PPDU is an intra-BSS PPDU with respect to the STA), the STAdetermines whether the first PPDU is received as an immediate responseto a second PPDU previously transmitted by the STA (decision block 430).In one embodiment, the STA determines whether the first PPDU is receivedas an immediate response to the second PPDU previously transmitted bythe STA based on a determination of whether the first PPDU is received aSIFS time after transmitting the second PPDU. For example, if the firstPPDU is received a SIFS time after transmitting the second PPDU, the STAmay determine that the first PPDU is received as an immediate responseto the second PPDU. In one embodiment, the STA determines whether thefirst PPDU is received as an immediate response to the second PPDUpreviously transmitted by the STA based on one or more indicationsincluded in an L-SIG field or HE-SIG-A field (e.g. BSS color) of thepreamble portion of the first PPDU. For example, the STA may have someidea regarding the expected characteristics and length of the type offrame that it should receive in response to transmitting the secondPPDU. Based on the above information (e.g., length of the first PPDU orexpected response and indications included in the L-SIG/SIG-A fields),the STA may determine that the received PPDU (e.g., the first PPDU) isan immediate response to the second PPDU without having the informationin the TA/RA fields of the second PPDU. In one embodiment, the secondPPDU previously transmitted by the STA includes trigger information thatelicits an immediate response from one or more other STAs.

If the STA determines that the first PPDU is received as an immediateresponse to the second PPDU previously transmitted by the STA, the APrefrains from setting/updating a NAV maintained by the STA (block 470).However, if the STA determines that the first PPDU is not received as animmediate response to the second PPDU previously transmitted by the STA,the STA determines whether the duration indicated in the control fieldof the preamble portion of the first PPDU is greater than a current NAVvalue (decision block 440). If so, the STA updates the NAV maintained bythe STA using the duration indicated in the control field of thepreamble portion of the first PPDU (block 450). In one embodiment, theduration is indicated in a TXOP duration field of the control field ofthe preamble portion of the first PPDU. In one embodiment, the controlfield of the preamble portion of the first PPDU is an HE-SIG-A field.

Returning to decision block 420, if the STA determines that the BSScolor indicated in the first PPDU does not match the BSS color of theBSS that the STA is associated with (e.g., first PPDU is an inter-BSSPPDU with respect to the STA), then the STA determines whether thereceived power level of the first PPDU is greater than a predeterminedpower level (decision block 460). If the received power level is notgreater than the predetermined power level, then the STA refrains fromsetting/updating the NAV maintained by the STA (block 470).

In this case, the STA may determine that the wireless medium is idle fortransmitting a PPDU (e.g., ready for SR). However, if the received powerlevel is greater than the predetermined power level, then the STAupdates the NAV maintained by the STA using the duration indicated inthe control field of the preamble portion of the first PPDU (block 450)when the duration is greater than the current NAV value (see decisionblock 440). In one embodiment, the predetermined power level is an OBSSPD level.

As previously mentioned, an AP may initiate a UL MU simultaneoustransmission by transmitting a trigger frame to a set of STAs that areto participate in the UL MU simultaneous transmission. The AP mayinitiate multiple UL MU simultaneous transmission within a given TXOP bytransmitting multiple trigger frames within the TXOP, where differenttrigger frames may elicit UL MU simultaneous transmission from differentsets of STAs. For example, the first trigger frame may elicit UL MUsimultaneous transmission from STA1 and STA2, the second trigger framemay elicit UL MU simultaneous transmission from STA3 and STA4, and thethird trigger frame may elicit UL MU simultaneous transmission fromSTA3, STA4, and STAS.

According to current 802.11 specification, a STA that receives a triggerframe that elicits the STA to participate in a UL MU simultaneoustransmission considers its NAV when determining whether to respond tothe trigger frame unless one of the following conditions is met: 1) NAVwas set by a frame originating from the AP that transmitted the triggerframe; and 2) the response includes ACK/BA frame and the duration of theUL MU simultaneous transmission is below a predetermined threshold. Insome cases, the STA may have set its NAV based on receiving a PPDU whichhas a payload error (e.g., and thus the STA is unable to obtaininformation from TA/RA fields). In these cases, following current rules,the STA may consider its NAV when it decides whether to respond to atrigger frame that elicits the STA to participate in a UL MUsimultaneous transmission. This can result in inefficient operation in aWLAN (e.g., HEW), as described below.

FIG. 5 is a diagram illustrating a scenario where a STA does not respondto a trigger frame due to its NAV being set, according to someembodiments. In this exemplary scenario, the AP transmits an RTS frameto STA1 and STA2. The AP then receives CTS frames from STA1 and STA2 aspart of a UL MU simultaneous transmission. The exchange of the RTS andCTS frames helps avoid any hidden node problems.

The AP then transmits a trigger frame to STA1 and STA2 that elicits anUL MU simultaneous transmission from those STAs. In response, STA1 andSTA2 transmit an UL MU PPDU to the AP, where the UL MU PPDU includes apreamble portion and a payload portion. In this example, STA3 does notdetect the RTS frame, the CTS frames, or the trigger frame or STA3detects the RTS frame, the CTS frames, or the trigger frame incorrectly.STA3 is able to successfully decode the preamble portion of the UL MUPPDU, but is unable to successfully decode the payload portion of the ULMU PPDU due to an error. As such, STA3 is unable to obtain informationincluded in the RA/TA fields. STA3 may thus set its NAV using theduration indicated in the preamble portion of the UL MU PPDU. The AP maythen transmit a trigger frame to STA3 and STA4 that elicits an UL MUsimultaneous transmission from those STAs. However, STA3 may not respondto this trigger frame due to its NAV being set. This is not an intendedprocedure.

To address this problem, in one embodiment, when a STA receives a PPDUthat elicits a UL MU simultaneous transmission from the STA (e.g., thePPDU includes a trigger frame or trigger information), the STA respondsto the PPDU after xIFS time without regard to its NAV if its NAV was setusing a duration indicated in a duration field of a control field of anintra-BSS PPDU originating from an unknown source. The source could beunknown to the STA because the STA is unable to successfully decode thepayload portion of the PPDU (and more specifically, the TA/RA fields ofthe MAC header). However, the STA may determine that the PPDU is anintra-BSS PPDU based on successfully decoding the preamble portion ofthe PPDU, which may include an indication of the BSS color. In oneembodiment, the PPDU that elicits the UL MU simultaneous transmissionfrom the STA includes a trigger frame. In one embodiment, the durationfield is a TXOP duration field of the control field. In one embodiment,the control field is an HE-SIG-A field. In one embodiment, the unknownsource can be a non-TXOP holder.

For example, as shown in FIG. 6, which corresponds to the scenariodescribed with reference to FIG. 5, when STA3 receives the secondtrigger frame, STA3 responds by transmitting a UL MU PPDU without regardto its NAV because its NAV was set using a duration indicated in a PPDUoriginating from an unknown source (e.g., source of initial UL MU PPDUis unknown to STA3 due to STA3 not being able to successfully decode thepayload portion of the initial UL MU PPDU).

FIG. 7 is a flow diagram of a process for using a NAV, according to someembodiments. In one embodiment, the operations of the flow diagram maybe performed by a network device functioning as a non-AP STA in awireless communications network (e.g., a WLAN).

In one embodiment, the process is initiated when the STA receives afirst PPDU from an AP, where the first PPDU elicits an immediateresponse from the STA (block 710). In one embodiment, the first PPDUincludes trigger information (e.g., a trigger frame) that elicits theSTA to participate in a UL MU simultaneous transmission.

The STA determines whether a NAV maintained by the STA was previouslyset using a duration indicated in a second PPDU that originated from thesame BSS as the BSS that the STA is associated with (block 720). The STAmay have determined that the second PPDU originated from the same BSS asthe BSS that the STA is associated with based on determining that theBSS color indicated in the preamble portion of the second PPDU (e.g., inthe control field of the preamble portion of the second PPDU) matchesthe BSS color of the BSS associated with the STA even if the STA wasunable to successfully decode the payload portion of the second PPDU. Ifthe STA determines that the NAV maintained by the STA was not previouslyset using the duration indicated in the second PPDU that originated fromthe same BSS as the BSS that the STA is associated with, the STAconsiders NAV when deciding whether to transmit a response to the firstPPDU, given that other conditions for ignoring NAV do not apply (block730). However, if the STA determines that the NAV maintained by the STAwas previously set using the duration indicated in the second PPDU thatoriginated from the same BSS as the BSS that the STA is associated with,the STA transmits a third PPDU to the AP as an immediate response to thefirst PPDU without regard for the NAV maintained by the STA (block 740).In one embodiment, the duration is indicated in a TXOP duration field ofan HE-SIG-A field of a preamble portion of the second PPDU. In oneembodiment, the STA transmits the third PPDU to the AP a SIFS time afterreceiving the first PPDU.

FIG. 8 is a block diagram of a network device implementing a STA or APthat executes a NAV component, according to some embodiments. In awireless local area network (WLAN) such as the example WLAN illustratedin FIG. 9, a basic service set (BSS) includes a plurality of networkdevices referred to herein as WLAN devices. Each of the WLAN devices mayinclude a medium access control (MAC) layer and a physical (PHY) layeraccording to IEEE 802.11 standard. In the plurality of WLAN devices, atleast one WLAN device may be an AP station (e.g., access point 0 andaccess point 1 in FIG. 9) and the other WLAN devices may be non-APstations (non-AP STAs), (e.g., stations 0-3 in FIG. 9). Alternatively,all of the plurality of WLAN devices may be non-AP STAs in an Ad-hocnetworking environment. In general, the AP STA and the non-AP STA may beeach referred to herein as a station (STA). However, for ease ofdescription, only the non-AP STA will be referred to herein as a STAwhereas the AP stations are referred to herein as APs for ease ofdescription. As shown in FIG. 9, a WLAN can have any combination of STAsand APs that can form a discrete network, an ad hoc network or anycombination thereof. Any number of APs and STAs can be included in aWLAN and any topology and configuration of such APs and STAs in thenetwork can be utilized.

The example WLAN device 1 includes a baseband processor 10, a radiofrequency (RF) transceiver 20, an antenna unit 30, memory 40, an inputinterface unit 50, an output interface unit 60, and a bus 70. Thebaseband processor 10 performs baseband signal processing, and includesa MAC processor 11 and a PHY processor 15. These processors can be anytype of integrated circuit (IC) including a general processing unit oran application specific integrated circuit (ASIC). In some embodiments,the MAC processor 11 also implements a NAV component 800. The NAVcomponent 800 can implement the respective functions for any combinationof the embodiments described herein above with regard to FIGS. 1-7. Inother embodiments, the NAV component 800 may be implemented by ordistributed over both the PHY processor 15 and the MAC processor 11. TheNAV component 800 may be implemented as software or as hardwarecomponents of either the PHY processor 15 or MAC processor 11.

In one embodiment, the MAC processor 11 may include a MAC softwareprocessing unit 12 and a MAC hardware processing unit 13. The memory 40may store software (hereinafter referred to as “MAC software”),including at least some functions of the MAC layer. The MAC softwareprocessing unit 12 executes the MAC software to implement some functionsof the MAC layer and the MAC hardware processing unit 13 may implementthe remaining functions of the MAC layer in hardware (hereinafterreferred to “MAC hardware”). However, the MAC processor 11 is notlimited to this distribution of functionality.

The PHY processor 15 includes a transmitting signal processing unit 100and a receiving signal processing unit 200 described further hereinbelow with reference to FIGS. 9 and 10.

The baseband processor 10, the memory 40, the input interface unit 50,and the output interface unit 60 may communicate with each other via thebus 70. The radio frequency (RF) transceiver 20 includes an RFtransmitter 21 and an RF receiver 22. The memory 40 may further store anoperating system and applications. In some embodiments, the memory maystore recorded information about captured frames. The input interfaceunit 50 receives information from a user and the output interface unit60 outputs information to the user.

The antenna unit 30 includes one or more antennas. When a MIMO orMU-MIMO system is used, the antenna unit 30 may include a plurality ofantennas.

FIG. 10 is a schematic block diagram exemplifying a transmitting signalprocessor in a WLAN device, according to some embodiments. Referring tothe above drawing, a transmitting signal processing unit 100 includes anencoder 110, an interleaver 120, a mapper 130, an inverse Fouriertransformer (IFT) 140, and a guard interval (GI) inserter 150. Theencoder 110 encodes input data. For example, the encoder 110 may be aforward error correction (FEC) encoder. The FEC encoder may include abinary convolutional code (BCC) encoder followed by a puncturing deviceor may include a low-density parity-check (LDPC) encoder.

The transmitting signal processing unit 100 may further include ascrambler for scrambling the input data before encoding to reduce theprobability of long sequences of 0s or 1s. If BCC encoding is used inthe encoder 110, the transmitting signal processing unit 100 may furtherinclude an encoder parser for demultiplexing the scrambled bits among aplurality of BCC encoders. If LDPC encoding is used in the encoder 110,the transmitting signal processing unit 100 may not use the encoderparser.

The interleaver 120 interleaves the bits of each stream output from theencoder to change the order of bits. Interleaving may be applied onlywhen BCC encoding is used. The mapper 130 maps the sequence of bitsoutput from the interleaver to constellation points. If LDPC encoding isused in the encoder 110, the mapper 130 may further perform LDPC tonemapping in addition to constellation mapping.

When multiple input-multiple output (MIMO) or multiple user (MU)-MIMO isused, the transmitting signal processing unit 100 may use a plurality ofinterleavers 120 and a plurality of mappers 130 corresponding to thenumber Nss of spatial streams. In this case, the transmitting signalprocessing unit 100 may further include a stream parser for dividingoutputs of the BCC encoders or the LDPC encoder into blocks that aresent to different interleavers 120 or mappers 130. The transmittingsignal processing unit 100 may further include a space-time block code(STBC) encoder for spreading the constellation points from the Nssspatial streams into NSTS space-time streams and a spatial mapper formapping the space-time streams to transmit chains. The spatial mappermay use direct mapping, spatial expansion, or beamforming.

The IFT 140 converts a block of the constellation points output from themapper 130 or the spatial mapper to a time domain block (i.e., a symbol)by using an inverse discrete Fourier transform (IDFT) or an inverse fastFourier transform (IFFT). If the STBC encoder and the spatial mapper areused, the inverse Fourier transformer 140 may be provided for eachtransmit chain.

When MIMO or MU-MIMO is used, the transmitting signal processing unit100 may insert cyclic shift diversities (CSDs) to prevent unintentionalbeamforming. The CSD insertion may occur before or after the inverseFourier transform 140. The CSD may be specified per transmit chain ormay be specified per space-time stream. Alternatively, the CSD may beapplied as a part of the spatial mapper. When MU-MIMO is used, someblocks before the spatial mapper may be provided for each user.

The GI inserter 150 prepends a GI to the symbol. The transmitting signalprocessing unit 100 may optionally perform windowing to smooth edges ofeach symbol after inserting the GI. The RF transmitter 21 converts thesymbols into an RF signal and transmits the RF signal via the antennaunit 30. When MIMO or MU-MIMO is used, the GI inserter 150 and the RFtransmitter 21 may be provided for each transmit chain.

FIG. 11 is a schematic block diagram exemplifying a receiving signalprocessing unit in the WLAN device, according to some embodiments.Referring to FIG. 11, a receiving signal processing unit 200 includes aGI remover 220, a Fourier transformer (FT) 230, a demapper 240, adeinterleaver 250, and a decoder 260.

An RF receiver 22 receives an RF signal via the antenna unit 30 andconverts the RF signal into symbols. The GI remover 220 removes the GIfrom the symbol. When MIMO or MU-MIMO is used, the RF receiver 22 andthe GI remover 220 may be provided for each receive chain.

The FT 230 converts the symbol (i.e., the time domain block) into ablock of constellation points by using a discrete Fourier transform(DFT) or a fast Fourier transform (FFT). The Fourier transformer 230 maybe provided for each receive chain.

When MIMO or MU-MIMO is used, the receiving signal processing unit 200may use a spatial demapper for converting the Fourier transformedreceiver chains to constellation points of the space-time streams and anSTBC decoder for despreading the constellation points from thespace-time streams into the spatial streams.

The demapper 240 demaps the constellation points output from the Fouriertransformer 230 or the STBC decoder to bit streams. If LDPC encoding isused, the demapper 240 may further perform LDPC tone demapping beforeconstellation demapping. The deinterleaver 250 deinterleaves the bits ofeach stream output from the demapper 240. Deinterleaving may be appliedonly when BCC encoding is used.

When MIMO or MU-MIMO is used, the receiving signal processing unit 200may use a plurality of demappers 240 and a plurality of deinterleavers250 corresponding to the number of spatial streams. In this case, thereceiving signal processing unit 200 may further include a streamdeparser for combining the streams output from the deinterleavers 250.

The decoder 260 decodes the streams output from the deinterleaver 250 orthe stream deparser. For example, the decoder 260 may be an FEC decoder.The FEC decoder may include a BCC decoder or an LDPC decoder. Thereceiving signal processing unit 200 may further include a descramblerfor descrambling the decoded data. If BCC decoding is used in thedecoder 260, the receiving signal processing unit 200 may furtherinclude an encoder deparser for multiplexing the data decoded by aplurality of BCC decoders. If LDPC decoding is used in the decoder 260,the receiving signal processing unit 200 may not use the encoderdeparser.

FIG. 12 is a timing diagram providing an example of the Carrier SenseMultiple Access/Collision Avoidance (CSMA/CA) transmission procedure,according to some embodiments. In the illustrated example, STA1 is atransmit WLAN device for transmitting data, STA2 is a receive WLANdevice for receiving the data, and STA3 is a WLAN device, which may belocated at an area where a frame transmitted from the STA1 and/or aframe transmitted from the STA2 can be received by the WLAN device.

STA1 may determine whether the channel is busy by carrier sensing. TheSTA1 may determine the channel occupation based on a quality of thesignal on the channel or correlation of signals in the channel, or maydetermine the channel occupation by using a NAV timer.

When determining that the channel is not used by other devices duringDIFS (that is, the channel is idle), STA1 may transmit an RTS frame toSTA2 after performing backoff. Upon receiving the RTS frame, STA2 maytransmit a CTS frame as a response of the CTS frame after SIFS. WhenSTA3 receives the RTS frame, it may set the NAV timer for a transmissionduration of subsequently transmitted frames (for example, a duration ofSIFS+CTS frame duration+SIFS+data frame duration+SIFS+ACK frameduration) by using duration information included in the RTS frame. WhenSTA3 receives the CTS frame, it may set the NAV timer for a transmissionduration of subsequently transmitted frames (for example, a duration ofSIFS+data frame duration+SIFS+ACK frame duration) by using durationinformation included in the CTS frame. Upon receiving a new frame beforethe NAV timer expires, STA3 may update the NAV timer by using durationinformation included in the new frame. STA3 does not attempt to accessthe channel until the NAV timer expires.

When STA1 receives the CTS frame from the STA2, it may transmit a dataframe to the STA2 after SIFS elapses from a time when the CTS frame hasbeen completely received. Upon successfully receiving the data frame,the STA2 may transmit an ACK frame as a response of the data frame afterSIFS elapses.

When the NAV timer expires, STA3 may determine whether the channel isbusy through the use of carrier sensing techniques. Upon determiningthat the channel is not used by other devices during DIFS and after theNAV timer has expired, STA3 may attempt channel access after acontention window according to random backoff elapses.

A PHY-RXSTART.indication primitive is an indication by the physicallayer (PHY) to the local MAC entity that the PHY has received a validstart of a PPDU, including a valid PHY header. This primitive isgenerated by the local PHY entity and provided to the MAC sublayer whenthe PHY has successfully validated a PHY header at the start of a newPPDU. This primitive provides the following parameters:

  PHY-RXSTART.indication(    RXVECTOR )The RXVECTOR parameter represents a list of parameters that the localPHY entity provides to the local MAC entity upon receipt of a valid PHYheader or upon receipt of the last PSDU data bit in a received frame.The RXVECTOR may include a TXOP_DURATION parameter that includesduration information.

After generating a PHY-RXSTART.indication primitive, the PHY is expectedto maintain a physical medium busy status during the period that ittakes for the PHY to transfer a frame of the indicated LENGTH at theindicated DATARATE. The physical medium busy status may be maintainedeven if a PHY-RXEND.indication(CarrierLost) primitive or aPHY-RXEND.indication(FormationViolation) primitive is generated by thePHY prior to the end of this period.

A PHY-RXEND.indication primitive is an indication by the PHY to thelocal MAC entity that the PSDU currently being received is complete.This primitive is generated by the local PHY entity and provided to theMAC sublayer to indicate that the receive state machine has completed areception with or without errors. This primitive provides the followingparameters:

  PHY-RXEND.indication(    RXERROR,    RXVECTOR )The RXERROR parameter can convey one or more of the following values:NoError, FormatViolation, CarrierLost, Unsupported Rate and Filtered. Anumber of error conditions may occur after the PHY's receive statemachine has detected what appears to be a valid preamble and Start FrameDelimiter (SFD). NoError is a value used to indicate that no erroroccurred during the receive process in the PHY. FormatViolation is avalue used to indicate that the format of the received PPDU was inerror. CarrierLost is a value used to indicate that the carrier was lostduring the reception of the incoming PSDU and no further processing ofthe PSDU can be accomplished. UnsupportedRate is a value that is used toindicate that a non-supported data rate was detected during thereception of the incoming PPDU. Filtered is a value used to indicatethat the incoming PPDU was filtered out during the reception of theincoming PPDU due to a condition set in the PHYCONFIG_VECTOR. In thecase of an RXERROR value of NoError, the MAC may use thePHY-RXEND.indication primitive as a reference for channel access timing.

The RXVECTOR parameter represents a list of parameters that the localPHY entity provides to the local MAC entity upon receipt of a valid PHYheader or upon receipt of the last PSDU data bit in a received frame.The RXVECTOR may include a TXOP_DURATION parameter that includesduration information. RXVECTOR may only be included whendot11RadioMeasurementActivated is true. This vector may contain both MACand MAC management parameters.

The solutions provided herein have been described with reference to awireless LAN system; however, it should be understood that thesesolutions are also applicable to other network environments, such ascellular telecommunication networks, wired networks, and similarcommunication networks.

An embodiment may be an article of manufacture in which a non-transitorymachine-readable medium (such as microelectronic memory) has storedthereon instructions which program one or more data processingcomponents (generically referred to here as a “processor”) to performthe operations described above. In other embodiments, some of theseoperations might be performed by specific hardware components thatcontain hardwired logic (e.g., dedicated digital filter blocks and statemachines). Those operations might alternatively be performed by anycombination of programmed data processing components and fixed hardwiredcircuit components.

Some portions of the preceding detailed descriptions have been presentedin terms of algorithms and symbolic representations of operations ondata bits within a computer memory. These algorithmic descriptions andrepresentations are the ways used by those skilled in conferencingtechnology to most effectively convey the substance of their work toothers skilled in the art. An algorithm is here, and generally,conceived to be a self-consistent sequence of operations leading to adesired result. The operations are those requiring physicalmanipulations of physical quantities. It should be borne in mind,however, that all of these and similar terms are to be associated withthe appropriate physical quantities and are merely convenient labelsapplied to these quantities. Unless specifically stated otherwise asapparent from the above discussion, it is appreciated that throughoutthe description, discussions utilizing terms such as those set forth inthe claims below, refer to the action and processes of a conferencedevice, or similar electronic computing device, that manipulates andtransforms data represented as physical (electronic) quantities withinthe conference device's registers and memories into other data similarlyrepresented as physical quantities within the conference device'smemories or registers or other such information storage, transmission ordisplay devices.

While the flow diagrams in the figures herein show a particular order ofoperations performed by certain embodiments, it should be understoodthat such order is exemplary (e.g., alternative embodiments may performthe operations in a different order, combine certain operations, overlapcertain operations, etc.).

While the invention has been described in terms of several embodiments,those skilled in the art will recognize that the invention is notlimited to the embodiments described, can be practiced with modificationand alteration within the spirit and scope of the appended claims. Thedescription is thus to be regarded as illustrative instead of limiting.

What is claimed is:
 1. A method implemented by a station (STA) in aWireless Local Area Network (WLAN) to disregard a Network AllocationVector (NAV) maintained by the STA, the method comprising: receiving afirst frame from an Access Point (AP); determining whether the NAVmaintained by the STA was previously set using a duration indicated in asecond frame that (1) was received by the STA prior to receiving thefirst frame and (2) originated from the AP; and transmitting a thirdframe to the AP as an immediate response to the first frame withoutconsidering the NAV maintained by the STA when a determination is madethat the NAV maintained by the STA was previously set using the durationindicated in the second frame that originated from the AP.
 2. The methodof claim 1, wherein the transmitting is performed with consideration tothe NAV maintained by the STA when a determination is made that the NAVmaintained by the STA was not previously set using the durationindicated in the second frame that originated from the AP.
 3. The methodof claim 1, wherein the first frame includes trigger information thatelicits the STA to participate in an uplink (UL) multi-user (MU)simultaneous transmission.
 4. The method of claim 3, wherein the firstframe is a trigger frame that includes the trigger information.
 5. Themethod of claim 1, wherein the duration is indicated in a transmitopportunity (TXOP) duration field of a control field of a preambleportion of the second frame.
 6. The method of claim 5, wherein thecontrol field is an HE-SIG-A field.
 7. The method of claim 1, whereinthe STA transmits the third frame to the AP an Interframe Space (IFS)time after receiving the first frame.
 8. The method of claim 7, whereinthe IFS time is a Short Interframe Space (SIFS) time.
 9. A stationoperating in a Wireless Local Area Network (WLAN), the stationcomprising: a set of one or more processors; and a non-transitorymachine-readable storage medium having stored therein instructions,which when executed by the set of one or more processors, causes thestation to: receive a first frame from an Access Point (AP); determinewhether a Network Allocation Vector (NAV) maintained by the station waspreviously set using a duration indicated in a second frame that (1) wasreceived by the station prior to receiving the first frame and (2)originated from the AP; and transmit a third frame to the AP as animmediate response to the first frame without considering the NAVmaintained by the station when a determination is made that the NAVmaintained by the station was previously set using the durationindicated in the second frame that originated from the AP.
 10. Thestation of claim 9, wherein the transmitting is performed withconsideration to the NAV maintained by the station when a determinationis made that the NAV maintained by the station was not previously setusing the duration indicated in the second frame that originated fromthe AP.
 11. The station of claim 9, wherein the first frame includestrigger information that elicits the station to participate in an uplink(UL) multi-user (MU) simultaneous transmission.
 12. The station of claim11, wherein the first frame is a trigger frame that includes the triggerinformation.
 13. The station of claim 9, wherein the duration isindicated in a transmit opportunity (TXOP) duration field of a controlfield of a preamble portion of the second frame.
 14. The station ofclaim 13, wherein the control field is an HE-SIG-A field.
 15. Thestation of claim 9, wherein the station transmits the third frame to theAP an Interframe Space (IFS) time after receiving the first frame. 16.The station of claim 15, wherein the IFS time is a Short InterframeSpace (SIFS) time.
 17. A non-transitory machine-readable medium storinginstructions, which when executed by one or more processors of a station(STA) in a Wireless Local Area Network (WLAN), causes the STA to:receive a first frame from an Access Point (AP); determine whether aNetwork Allocation Vector (NAV) maintained by the STA was previously setusing a duration indicated in a second frame that (1) was received bythe STA prior to receiving the first frame and (2) originated from theAP; and transmit a third frame to the AP as an immediate response to thefirst frame without considering the NAV maintained by the STA when adetermination is made that the NAV maintained by the STA was previouslyset using the duration indicated in the second frame that originatedfrom the AP.
 18. The non-transitory machine-readable medium of claim 17,wherein the transmitting is performed with consideration to the NAVmaintained by the STA when a determination is made that the NAVmaintained by the STA was not previously set using the durationindicated in the second frame that originated from the AP.
 19. Thenon-transitory machine-readable medium of claim 17, wherein the firstframe includes trigger information that elicits the STA to participatein an uplink (UL) multi-user (MU) simultaneous transmission, and whereinthe first frame is a trigger frame that includes the triggerinformation.
 20. The non-transitory machine-readable medium of claim 17,wherein the duration is indicated in a transmit opportunity (TXOP)duration field of an HE-SIG-A field of a preamble portion of the secondframe.